Poppet valve control



Jan. 17, 1933. c. s. BURNETT POPPET VALVE CONTROL I Filed June 1 8, 1929 INVENTOR ATTORNEY Patented Jan. 17, 1933 UNITED STATES CHARLES S. BURNETT, OF PRESIDIO OF SAN FRANCISCO, CALIFORNIA POPPIET VALVE CONTROL Application filed June 18,

1929. Serial No. 371,951.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRIL 39, 1928; 370 0. G. 757) This invention describedv herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to means for controlling poppet valves of engines and the like and more particularly to an articulated cam, the dwell or the circumferential extent of the swell of which is adapted to be varied by a governor control or its equivalent.

The cam proper is composed of two parts, one intended to be rigidly secured to the cam shaft and the other pivoted to the first mentioned part and capable of being swung thereabout to modify the cam contour.

The second mentioned cam member is adapted to be engaged by a pin, slidable in the first part, that is in turn contacted by a small cam carried by a hollow rod that is journalled within the hollow cam shaft. Relative movement of the shaft and rod is brought about by means of a governor which variations in the rate of rotation of the cam shaft are designed to affect. When the rod, rotated with respect'to the cam shaft, causes the cam on the rod to engage the pin, the lat ter is forced outwardly and carries therewith the pivoted cam segment whereby that portion of the cam surface represented by the pivoted segment is caused to assume a new position with respect to the fixed cam part resulting in a modification of the cam surface and the valve actuation accordingly. The design of the fixed and pivoted segment of the cam is such that in all relative positions thereof the contour is such that it presents to a follower designed to ride thereover, a smooth surface.

The invention is illustrated as embodying a ball governor as a means for effecting relative rotation of the rod with respect to the cam shaft but it is to be strictly borne in mind that I do not limit myself by so doing as apparatus to produce this relative rotation may be any means expedient foreifecting the desideratum.

One object of the invention is to provide a cam whose dwell may be varied automatically by the operation of the device in which it is embodied.

Another object of the invention is to provide a cam which operates to bring about a later rather than a slower closing of an engine intake valve with which it is associated.

A further object is to effect the object last mentioned without increasing or decreasing the lift of the valve.

Again another object is to produce such a cam thatis positively varied and brought back to its original shape with the smallest number of movable parts.

Finally it is one of the prime objects of the invention to produce a cam which is capable of being readily assembled and applied to the machine with which it is to be utilized.

In order that the invention may be thoroughly understood, reference is had to the accompanying drawing forming a part of this specification in which Fig. 1 is an assembled view in elevation of the cam and governor control therefor,

Fig. 2 is a section at 22 on Figure 1,

Fig. 3 is an elevation of the pivoted segment of the cam,

Fig. 4 is a fragmentary showing of the collar journal which carries the pin actuating cam, and

Fig. 5 represents the pin actuating cam proper.

Suitably journalled in an engine so as to be rotated thereby is a hollow cam shaft (1) carrying the governor mechanism, broadly designated as A, positioned thereon so as to be constrained to rotate with the cam shaft. Afiixed to the end of the cam shaft (1) is a disk (2) carrying standards (3) perpendicular to the disk and provided with eyes (4) designed to carry governor balls (5) by means of arms (6) pivoted in the eyes The arms carry fingers (7 which, when the balls recede from the shaft, are designed to impinge a plate (8) carried on the standards (3) and urged awayfrom disk (2) by helical springs (9) positioned around the standards. The plate (8) is fashioned with a screw-threaded opening at its center adapted to engage a hollow rod (10) that is journalled within the cam shaft (1) through the intermediary of collar journals (11), which may or may not be integral with the rod, and a step bearing (12),

the latter designed to permit the rods rotation but preclude lateral movement thereof. Movement of the fingers (7) while against plate (8) because of the threaded opening in the latter engaging the end of the threaded rod, brings about a rotation of the rod within the cam shaft.

One collar journal (11) positioned at the point where is located the valve actuating cam broadly designated as B, is fashioned out as at 13) for the reception of a pin actuating cam (14), which is intended to be-introduced into the cavity.

The valve actuating cam is comprised of a main part (15) designed to be fixed by a key or other means to the cam shaft and has pivoted thereto through the intermediary of a. pin (16) a segment (17) purposed to be movable about the said pivot to modify the cam contour and so fashioned that in all positions thereof there is presented to a cam follower (1%) a smooth surface on which to ride.

ollower (18) has no part in this invention and is generally illustrated for the purpose of showing the relation between the valve actuating cam and the follower carried by valve tappet (19).

The segment (17) is constructed with depending skirts (20) designed to bestride or overlie the part (15) when the segment is in what may be designated as its retracted position. The skirt is extendedas at (21) on both sides of the fixed cam part in order that in certain positions of the segment the skirt may :3 operate as a portion of the cam surface but so that in retracted position the skirt extension passes below the cam contour, the main part (22) of the segment receding into a depression (23) of such depth that in the retracted position of the segment the main part of the latter forms with the surface of the fixed part of the cam a smooth contour. The fixed cam part is drilled out at (25) for the reception of a screw-threaded hollow sleeve (26) that operates as a bearing for an axially movable pin (27) that is adapted to contact with the pin actuating cam (14) in certain of the relatii e positions of cam shaft (1) and rod (10).

in (27), at that end which contacts with the pin actuating cam (14), is constructed with an enlargement (28) which functions not only as a bearin surface but also as a shoulder against which a spring (29) positioned between sleeve (25) and shoulder (28) operates for the purpose of constraining the pin to normally contact with the pin actuating cam (14) or the collar journal according as either the former or the latter underlie the pin. The pin on its other end is furnished with a threaded hole (30) adapted to receive a T-head (31) designed to engage with hooks (32) positioned on the under side of the movable segment of the cam.

The opening in the fixed cam segment,

wherein are inserted the sleeve and its intimately associated elements, is of such size as to accommodate the swing of the pin actuating cam (14) and in no way interfere with relative rotation of the cam shaft and rod and the'inner surface of the shaft is cut away at this point to accommodate the cam in its oscillation. The pin actuating cam (14) is preferably disassociated from or in other words, not integral with the annular collar (11) wherein it is designed to be positioned, for the purpose of facilitating the assemblage of the cam elements.

It can be readily seen that, with the construction above described, movement of cam (14) beneath pin (27) brings about a forcing of the pin outwardly with consequent like movement of segment (17) about its pivot, resulting in a variation or modification of the contour of the cam. As soon as relative rotation of shaft and rod operate to move cam (14) from a position of greatest pin lift to one of lesser extent, spring (29) effects a retraction of the pin and likewise segment 17).

For the purpose of lubricating the journals and'step bearing of rod (10) the latter is made hollow so that oil' may be introduced therein by any means expedient, the oil passing from the step bearing back to the journals on the other side of the rod or introduced directly to the journals throughoil holes formed within the rod according as either method appears the most expedient or desirable.

In assembling the cam on the cam shaft the fixed segment is first positioned after which pin actuatin cam (14) spring (29),pin (27) and sleeve 25) are introduced through the opening in the fixed cam segment. Subsequently movable cam segment (17 is hooked under T-head (31) which has previously been introduced into pin (27 and thereafter the pivot pin (16) is passed through the skirt of the cam segment and into the fixed segment of the cam thereby securing the segments of the main valve actuating cam in position.

In the operation of the device radial movement of the balls brought about through fluctuations in the engine speed, efli'ects through fingers (7 and springs (9) an axialmovement of plate 8) and in consequence of the latters threaded engagement with rod (10), a rotation of the rod with respect to the cam shaft. Rotation of the rod brings pin actuating cam to bear against pin (27) to produce movement of cam segment 17) as described supra.

From the foregoing description it is obvious that the invention is particularly adapted to the control of engine valves, because of the fact that any number of cams are susceptible of being positioned on the same cam shaft in diverse angular relation and when so stationed are capable of being influenced by the same actuatingrod through a multiplicity of pin actuating cams provided thereon.

Having described my invention, what I claim as new and wish to secure by Letters Patent is 1. In a sectional cam, a fixed part and a movable part pivoted thereto and having a skirt bestriding the fixed part, and an extension on said skirt operating in certain positions to form a portion of the cam contour of the said fixed part.

2. In an articulated cam, a fixed part, a movable part pivoted to the latter, hooks on said last mentioned part and means including a slidable pin engaging said hooks and a cam for operating said pin to effect operation of said movable part.

3. In a device of the class described, a fixed and a movable cam part, a hollow shaft on which said fixed part is positioned, a rod journalled within said shaft, and means including a cam whereby relative rotation of said shaft and rod effects movement of the second mentioned cam part with respect to the other.

4:. In a device of the class described an ar ticulated cam having a fixed part and a movable part, a hollow shaft to which said first part is fixed, a rod journalled within said shaft and means including a cam whereby relative rotation of said shaft and rod causes change of position of said movable cam part with respect to said fixed cam part.

5. In a device of the class described a fixed cam part adapted to be positioned upon a hollow shaft, a movable cam part pivoted to the fixed cam part, a rod journalled within said shaft, a cam on said rod, and means whereby relative rotation of said shaft and rod effects through said last mentioned cam, movement of the movable cam part with respect to the fixed cam part.

6. In a device of the class described, a fixed cam, a cam segment pivoted to said first mentioned cam, and means including a pin operatively connected to said pivoted cam segment and a spring encircling said pin and restraining the same to oppose pivotal movement of said cam segment about said cam.

7 In an articulated cam, a fixed part, a

movable part pivoted to the latter and means including a radially disposed cam actuated reciprocating pin for effecting relative movement of the two said parts.

CHARLES S. BURNETT. 

